<!DOCTYPE html>
<!--
	来源： https://www.zhangxinxu.com/wordpress/2019/08/css-flex-last-align/
-->
<html>

	<head>
		<meta charset="UTF-8">
		<title></title>
		<style>
			.container {
				display: flex;
				flex-wrap: wrap;
			}
			
			.list {
				width: 24%;
				height: 100px;
				background-color: skyblue;
				margin-top: 15px;
			}
			
			.list:not(:nth-child(4n)) {
				margin-right: calc(4% / 3);
			}
		</style>
	</head>

	<body>
		<div class="container">
			<div class="list"></div>
			<div class="list"></div>
			<div class="list"></div>
			<div class="list"></div>
			<div class="list"></div>
			<div class="list"></div>
			<div class="list"></div>
		</div>
	</body>

</html>